Field of the Invention
The present invention relates to liquid pumps. More particularly, the present invention relates to gas pressure and vacuum driven liquid pumps suitable for high purity and sterile liquid pumping applications.
Description of the Related Art
In many critical applications, there is a need for liquid transfer where the transferred liquid must be very carefully handled so as not to compromise the purity, physical, chemical, biological, or pharmaceutical characteristics of the liquid. One common issue in such applications is the need to maintain the cleanliness of the pumping equipment, always with an eye on the cost and downtime needed to maintain such equipment. By way of example, the biopharmaceutical industry is shifting to more single use equipment to reduce cost and increase flexibility in the manufacturing processes. Experience in the industry has demonstrated that cleaning and sterilization utilities, as well as validation and maintenance of the systems, are found to be more expensive than operating with single use equipment. With respect to single use pumping equipment, peristaltic pumps have been generally used as single use pumps since the tubing utilized in these pumps can be threaded through the pump head without breaching the sanitary barrier of the tube set. Peristaltic pumps are suitable for rough applications where process flow control is not of critical importance. However, many processes rely on more accurate flow control. Such systems have not yet been fully transitioned into the single use paradigm for this reason alone.
There are a number of other applications for single use pumps in the biopharmaceutical, and other, industries. For example, it is sometimes necessary to circulate liquids stored in a single use vessel, such as a polymeric lined storage vessel. In the prior art, single use mixing vessels have employed impellers within the liner that are driven through the liner by a magnetically coupled drive unit. This approach drives up the cost of the liner and creates material recycling issues with respect to the rare earth materials, such as neodymium, used in the magnet. Shipping liners with impellers inside is a packaging challenge as well. Liners are often found to leak from where the impeller has vibrated against the film.
In other applications, biopharmaceutical pumps need to provide ultra low shear so as to be gentle on sensitive product, provide a turndown greater than 100:1, operate under pressure ranges from 0.01 to over 100 psig, be self priming, provide positive shut-off of process flow, provide bidirectional liquid flow, provide very low pressure pulse and surge flow, and provide a flexible programming interface for processing considerations. Thus it can be appreciated that there is a need in the art for a liquid pump that address these, and other, problems in the prior art.